let form = new Form(Text = "F# Windows Form",
                    Visible = true,
                    TopMost = true)
form.MouseMove
    |> Event.map (fun evArgs -> (evArgs.X, evArgs.Y))
    |> Event.add ( fun (x, y) ->
        form.BackColor <- System.Drawing.Color.FromArgb(
            x, y, x ^^^ y) )